1. Field of the Invention
This invention pertains generally to hydraulic motors, and more particularly to an orifice motor for use as a down hole motor in association with a drill string for drilling wells.
2. Description of the Background Art
Hydraulic motors are widely used in many industrial applications, including downhole motors for oil, gas, and water well drilling. Generally, hydraulic downhole motors are of the turbine and progressing cavity or Moineau types, although vane type motors may also be used. These motors are typically powered by high pressure fluids introduced to the motor from the surface through a drill string. After exiting the motor, the fluid can be directed to the drill bit to aid in displacement and removal of particulate debris loosened by action of the drill bit. Electric motors have occasionally been used in downhole applications, but suffer problems associated with the substantial lengths of insulated conductors and remote electrical connections involved.
A variety of hydraulic motors have been previously developed. For example, U.S. Pat. No. 4,260,167 discloses a well drilling tool having a shaft rotationally related to a casing, each of which includes a plurality of rotors in a turbine section. As fluid is forced through the rotors, the shaft is driven.
U.S. Pat. No. 3,971,450 discloses a turbodrill having turbine blades included on a casing and a shaft which rotationally driven by fluids passing through.
German Patent No. 697,466 discloses a compressed air drill-hammer having a rotor that emits compressed gas at an angle, thereby imparting hammer motion and rotational motion to a shaft.
Canadian Patent No. 961,026 discloses a turbodrill having multiple rotors through which fluid passes for rotational motion. The rotor angles can be varied to provide hydrodynamic braking. U.S.S.R. Inventor Certificate No. 299,176 discloses the same turbodrill.
British Patent No. 1,109,875 discloses a hydraulic turbine for bore hole drilling having a sleeve and a shaft which each have turbine blades. When fluid passes through the turbine blades, rotational motion is provided to the shaft.
As can be seen therefore, several hydraulic motors for drilling purposes have been devised. However, currently available hydraulic downhole motors experience drawbacks which require frequent and expensive repair, resulting in lost time on drilling rigs. Particularly, high operating temperatures due to internal friction as well as use in high temperature wells leads to increased wear and failure of dynamic elastomeric parts within the motors. Progressing cavity or Moineau-design hydraulic motors are perhaps the most susceptible to heat related failure due to the substantial amounts of elastomeric material in the stator portion of the motor which are subjected to dynamic forces.
Therefore, there is a need for a hydraulic motor which is resistant to wear and failure at high operating temperatures, and which does not require frequent repair. The present invention satisfies these needs, as well as others, and overcomes the deficiencies found in existing hydraulic motors.
The foregoing patents reflect the state of the art of which the applicant is aware and are tendered with the view toward discharging applicant's acknowledged duty of candor in disclosing information which may be pertinent in the examination of this application. It is respectfully stipulated, however, that none of these patents teach or render obvious, singly or when considered in combination, applicant's claimed invention.